logo - 刷刷题
下载APP
【简答题】

Immediately after the Civil War, however, the diet began to change. 61) Rail transportation increased the supply and improved the quality of the milk that reached centers; cold storage and refrigerator cars made possible the greater consumption of fresh vegetables, fresh fruits, and fresh fish; and commercial canning extended the range of appetizing and healthful foods. Subsequently food statistics indicated an increased consumption of dairy products, fresh fruits, fresh vegetables, sugar and syrups, coffee, tea, cocoa, and spices. Decreased consumption was shown for meats, potatoes, and grain products. 62) By and large, the American diet continued to reflect a considerable reliance upon animal products, rather than on grains, which meant that a relatively large acreage was required to feed the American public. Whereas a grain and fish diet, such as in Japan, requires only a quarter of an acre high-yield cropland and no pasture per capita, the American diet requires about two and a half acres of cropland and ten acres of pasture per capita. Also it indicated a shift toward the so-called protective foods, toward those high in vitamins and proteins. 63) This change was greatly furthered by governmental food inspection (the Pure Food and Drug Act was passed in 1906), by the increasing use of mechanical refrigerators in the 1920’s and 1930’s and of freezers for frozen food during recent decades.
In the years after World War I a food revolution took place that’ was reminiscent of the one that occured after the Civil War. The output of the food-manufacturing industry quadrupled from 1900 to 1940. ) In that interval, as we have mentioned earlier, home canning gave way to commercial canning, and the labor of housekeeping was lightened.
Fortunately most of the major dietary changes that have taken place since the middle of the nineth century have resulted in better nutrition for the population. In part, these shifts have taken place because of a preference for new foods rather than old, but in part, they have been made because the new foods were advocated by nutritionists. Apparently American dietary customs were not so deeply ingrained as to pr change in the interests of better health; 65) Possibly one factor that has contributed to the readiness of Americans to accept new foods or food preparations is the general familiarity with a variety of regional dishes coming from many different lands. Within a small area in New York City or San Francisco, one can find restaurants specializing in French, Italian, German, Turkish, Ar, or Chinese cuisine. And at a Chinese restaurant in the United States the chef and waiter are as likely as not to be Oriental.

Rail transportation increased the supply and improved the quality of the milk that reached centers; cold storage and refrigerator cars made possible the greater consumption of fresh vegetables, fresh fruits, and fresh fish; and commercial canning extended the range of appetizing and healthful foods.

Immediately after the Civil War, however, the diet began to change. 61) Rail transportation increased the supply and improved the quality of the milk that reached centers; cold storage and refrigerator cars made possible the greater consumption of fresh vegetables, fresh fruits, and fresh fish; and commercial canning extended the range of appetizing and healthful foods. Subsequently food statistics indicated an increased consumption of dairy products, fresh fruits, fresh vegetables, sugar and syrups, coffee, tea, cocoa, and spices. Decreased consumption was shown for meats, potatoes, and grain products. 62) By and large, the American diet continued to reflect a considerable reliance upon animal products, rather than on grains, which meant that a relatively large acreage was required to feed the American public. Whereas a grain and fish diet, such as in Japan, requires only a quarter of an acre high-yield cropland and no pasture per capita, the American diet requires about two and a half acres of cropland and ten acres of pasture per capita. Also it indicated a shift toward the so-called protective foods, toward those high in vitamins and proteins. 63) This change was greatly furthered by governmental food inspection (the Pure Food and Drug Act was passed in 1906), by the increasing use of mechanical refrigerators in the 1920’s and 1930’s and of freezers for frozen food during recent decades.
In the years after World War I a food revolution took place that’ was reminiscent of the one that occured after the Civil War. The output of the food-manufacturing industry quadrupled from 1900 to 1940. ) In that interval, as we have mentioned earlier, home canning gave way to commercial canning, and the labor of housekeeping was lightened.
Fortunately most of the major dietary changes that have taken place since the middle of the nineth century have resulted in better nutrition for the population. In part, these shifts have taken place because of a preference for new foods rather than old, but in part, they have been made because the new foods were advocated by nutritionists. Apparently American dietary customs were not so deeply ingrained as to pr change in the interests of better health; 65) Possibly one factor that has contributed to the readiness of Americans to accept new foods or food preparations is the general familiarity with a variety of regional dishes coming from many different lands. Within a small area in New York City or San Francisco, one can find restaurants specializing in French, Italian, German, Turkish, Ar, or Chinese cuisine. And at a Chinese restaurant in the United States the chef and waiter are as likely as not to be Oriental.

举报
参考答案:
参考解析:
.
刷刷题刷刷变学霸
举一反三

【单选题】(76)处填()。 A.2356Kb/s B.3534Kb/s C.7069Kb/s D.1178Kb/s

A.
假设一个有3个盘片的硬盘,共有4个记录面,转速为7200rpm,盘面有效记录区域的外直径为30cm,内直径为10cm,记录位密度为250位/mm,磁道密度为8道/mm,每磁道分16个扇区,每扇区512字节,则该硬盘的非格式化容量和格式化容量约为 (75) ,数据传输率约为 (76) ,若一个文件超出一个磁道容量,剩下的部分 (77)

【单选题】(116)处填()。 A.32 B.64 C.128 D.256

A.
常规的数据加密标准DES采用 (115) 位有效密钥对 (116) 位的数据块进行加密。

【单选题】(122)处填()。 A.并发 B.双工 C.双重 D.并行

A.
发展容错技术可提高计算机系统的可靠性。利用元件冗余可保证在局部有故障的情况下系统的正常工作。带有热备份的系统称为 (122) 系统。它是 (123) ,因此只要有一个子系统能正常工作,整个系统仍能正常工作。
B.
当子系统只能处于正常工作和不工作两种状态时,我们可以采用图A的并联模型(见图 1-21),若单个子系统的可靠性都为0.8,图示的三个子系统并联后的系统的可靠性为 (124) 。当子系统能处于正常和不正常状态时,我们可以采用图B所示的表决模型(见图1-21),若图中有任何二个或三个子系统输出相同,则选择该相同的输出作为系统输出。设单个子系统的可靠性为0.8时,整个系统的可靠性为 (125) ;若单个子系统的可靠性为0.5,整个系统的可靠性为 (126)
C.

【单选题】(128)处填()。 A.1 B.2 C.3 D.4

A.
为提高数据传输的可靠性,可采用“冗余校验”的方法;海明码是常用的方法之一。在此方法中,若要求能检测出所有的双位错,并能校正单位错,则合法码字集中的码距至少为 (127) 。若原始数据的字长为5位,则采用海明码时其校验位至少为 (128) 位。
B.
对图1-22的图(a)所示系统,仅当部件1,部件2和部件3,全部正常工作时,系统才能正常工作。图中数字为各部件的可靠性,整个系统的可靠性近似为 (129) 。如果将部件2和部件3改成由两个器件构成,如图(b)所示,只要器件a和b中有一个正常就能使部件2正常工作,只要器件c和d中有一个正常就能使部件3正常工作。图中数字是各器件的可靠性,则部件2的可靠性是 (130) ,整个系统的可靠性近似为 (131)
C.

【单选题】(52)处填()。 A.需要专门的指令来表示程序中并发关系和控制并发执行 B.靠指令本身就可以启动多个处理单元并行工作 C.只执行没有并发约束关系的程序 D.先并行执行,事后再用专门程序去解决并发约束

A.
利用并行处理技术可以缩短计算机的处理时间,所谓并行性是指 (48) 。可以采用多种措施来提高计算机系统的并行性,它们可分成三类,即 (49)
B.
提供专门用途的一类并行处理机(亦称阵列处理机)以 (50) 方式工作,它适用于 (51) 。多处理机是目前较高性能计算机的基本结构,它的并行任务的派生是 (52)

【单选题】(121)处填()。 A.PGP B.SSL C.SHTTP D.SOCKS

A.
数字签名是一种网络安全技术,利用这种技术,接收者可以确定发送者的身份是否真实,同时发送者不能 (117) 发送的消息,接收者也不能 (118) 接收的消息。Kerberos是一种分布式环境下的 (119) 系统。为了防止重放攻击(Replay),它使用了一次性的 (120) 和时间戳。在公钥加密的情况下,用户必须警惕用于加密的公钥是否属于真正的接收者,为此必须使用数字证书。常用的数字证书格式有 (121) 证书和X.509证书。

【单选题】(123)处填()。 A.两子系统同时同步运行,当联机子系统出错时,它退出服务,由备份系统接替 B.备份系统处于电源开机状态,一旦联机子系统出错,立即切换到备份系统 C.两子系统交替处于工作和自检状态,当发现一子系统出错时,它不再交替到工作状态 D.两子系统并行工作,提高机器速度,一旦一个子系统出错,放弃并行工作

A.
发展容错技术可提高计算机系统的可靠性。利用元件冗余可保证在局部有故障的情况下系统的正常工作。带有热备份的系统称为 (122) 系统。它是 (123) ,因此只要有一个子系统能正常工作,整个系统仍能正常工作。
B.
当子系统只能处于正常工作和不工作两种状态时,我们可以采用图A的并联模型(见图 1-21),若单个子系统的可靠性都为0.8,图示的三个子系统并联后的系统的可靠性为 (124) 。当子系统能处于正常和不正常状态时,我们可以采用图B所示的表决模型(见图1-21),若图中有任何二个或三个子系统输出相同,则选择该相同的输出作为系统输出。设单个子系统的可靠性为0.8时,整个系统的可靠性为 (125) ;若单个子系统的可靠性为0.5,整个系统的可靠性为 (126)
C.